Daewoo ST Series Instruções de Operação descarregar pdf (Página 128)

(2) Speed control unit for governor system (All)

a) Introduction

Series speed control unit is an all electronic device designed to control engine speed with

fast and precise response to transient load changes. This closed loop control, when

connected to a proportional electric actuator and supplied with a magnetic speed sensor

signal, will control a wide variety of engines in an isochronous or droop mode.

The speed control unit are the engine STARTING FUEL and SPEED RAMPING

adjustments. The use of these features will minimize engine exhaust smoke experienced

prior to attaining engine operating speed.

Other features include adjustable droop and idle operation, inputs for accessories used in

multi-engine or special applications, protection against reverse battery voltage, transient

voltages, accidental short circuit of the actuator and fail safe design in the event of loss of

speed sensor signal or battery supply.

b) Description

Engine speed information for the speed control unit is usually received from a magnetic pick-

up sensor Any other signal generating device may be used provided the generated

frequency is proportional to engine speed and meets the voltage input and frequency range

specification. The speed sensor is typically mounted in close proximity to an engine driven

ferrous gear, usually the engine ring gear. As the teeth of the gear pass the magnetic sensor,

a signal is generated which is proportional to engine speed.

Signal strength must be within the range of the input amplifier. An amplitude of 0.5 to 120 volts

RMS is required to allow the unit to function within its design specifications. The speed signal

is applied to Terminals C and D of the speed control unit. Between these terminals there is

an input impedance of over 33,000 ohms. Terminal D is internally connected to Terminal E,

battery negative. Only one end of the cable should be connected.

When a speed sensor signal is received by the controller, the signal is amplified and shaped

by an internal circuit to provide an analog speed signal. If the speed sensor monitor does not

detect a speed sensor signal, the output circuit of the speed control unit will turn off all current

to the actuator.

A summing circuit receives the speed sensor signal along with the speed adjust set point

input. The speed range has a ratio of 8:1 and is adjusted with a 25 turn potentiometer. The

output from the summing circuit is the input to the dynamic control section of the speed control

unit. The dynamic control circuit, of which the gain and stability adjustments are part, has a

control function that will provide isochronous and stable performance for most engine types

and fuel systems.

The speed control unit circuit is influenced by the gain and stability performance adjustments.

The governor system sensitivity is increased with clockwise rotation of the gain adjustment.

The gain adjustment has a range of 33:1.

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AD136/T/TI AD086TI

GAC actuator model ACD 176A-24 ACE 175

Speed control unit model DWC-2000 ESD55500

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Daewoo ST Series Instruções de Operação Página 128